1. Field of the Invention
Exemplary aspects of the present disclosure relate to a method for initializing expended modules in PLC (Programmable Logic Controller) system mounted with one basic unit and a plurality of expended modules, whereby an initialization time of an entire PLC system can be optimized by accurately recognizing, by the one basic unit, completion of initialization of the plurality of expended modules, when the one basic unit initializes the plurality of expended modules.
2. Description of Related Art
Apparatuses for factory automation of various types have emerged concomitant with technical development in automation fields owing to sophisticated technologies.
A PLC (Programmable Logic Controller) system among the apparatuses for factory automation uses programmable memories for implementing various functions such as logic, sequence, timing, counting and computing through digital or analog input/output modules. The PLC system, a core element for factory automation, is one of the apparatuses configured to control various types of equipment, machines and processors in a factory, and very effective means configured to satisfy various requirements for factory automation.
FIG. 1 is a schematic block diagram illustrating a configuration of a PLC system applied to a method for initialization according to prior art.
Referring to FIG. 1, the PLC system generally includes one basic unit (100) including a computing device, and a plurality of expended modules (110-1, 110-2, . . . , 110-N) configured to perform a data communication operation with an external device in response to control of the computing device, where the one basic unit (100) and the plurality of expended modules (110-1, 110-2, . . . , 110-N) respectively include an interface module (not shown).
The interface modules respectively mounted on the one basic unit (100) and the plurality of expended modules (110-1, 110-2, . . . , 110-N) are connected in series, for example, where a predetermined data (IS) transmitted by the one basic unit (100) is sequentially transmitted to the plurality of expended modules (110-1, 110-2, . . . , 110-N), and the data (IS) transmitted by the plurality of expended modules (110-1, 110-2, . . . , 110-N) is sequentially transmitted to the one basic unit (100) via the plurality of expended modules (110-1, 110-2, . . . , 110-N) at a previous stage.
FIG. 2 is a signal flowchart illustrating an operation of a basic unit applied to a method for initialization according to prior art.
Referring to FIG. 2, the basic unit (100) generates an initialization signal for the plurality of expended modules (110-1, 110-2, . . . , 110-N), when there is a need to initialize the plurality of expended modules (110-1, 110-2, . . . , 110-N), and transmits the generated initialization signal (IS) to an expended module (110-1) (S200). The expended module (110-1) performs an initialization operation subsequent to transmission of an initialization request signal (IS) to a next expended module (110-2), when the initialization request signal (IS) is received.
Furthermore, the expended module (110-2) performs an initialization operation subsequent to transmission of an initialization request signal (IS) to a next expended module (110-3), and the next expended module (110-3) performs an initialization operation subsequent to transmission of an initialization request signal (IS) to a next expended module (110-4), and the initialization operations are completed until the initialization request signal (IS) is sequentially transmitted to an expended module (110-N) that is located at the last stage.
Under this circumstance, the basic unit (100) waits for a pre-set initialization required time (S202), where the pre-set initialization required time is set based on, for example, a required time of the initialization request signal (IS) to be transmitted to the expended module (110-N) that is located at the end, and an expended module that has the longest initialization required time among the plurality of expended modules (110-1, 110-2, . . . , 110-N).
The basic unit (100) determines that the initialization of the plurality of expended modules (110-1, 110-2, . . . , 110-N) has finished (S204), if the preset initialization required time lapses, and finishes the initialization operations.
Time required for performing the initialization operations may be changed depending on the circumstances of the plurality of expended modules (110-1, 110-2, . . . , 110-N). However, the abovementioned prior art suffers from disadvantages in that the basic unit (100) waits for the preset initialization required time to lapse, thereby generating unnecessary waiting time, even if initialization operations of the plurality of expended modules (110-1, 110-2, . . . , 110-N) are finished before the preset initialization required time lapses, whereby the initialization time cannot be optimized.